Performance Evaluation of NOMA and OFDMA in LEO Satellite Constellations

Low Earth Orbit (LEO) satellite constellations are emerging as a cornerstone of next-generation communication infrastructures, and their significance for Internet of Things (IoT) ecosystems continues to grow steadily. LEO satellites operate at considerably lower orbital altitudes, thereby mitigating signal propagation delays and significantly reducing communication latency. The adoption of advanced multiple access techniques is indispensable, as they have to manage scarce spectral resources while supporting the exponential growth in the number of connected devices. Such techniques are required not only to enhance spectral efficiency and maximize achievable throughput but also to ensure robust and reliable connectivity in highly dynamic and interference-prone LEO environments. Consequently, the selection and design of multiple access schemes represent a critical factor in determining the overall performance, scalability, and quality of service of LEO-based communication systems. This thesis investigates the performance of Non-Orthogonal Multiple Access (NOMA) and Orthogonal Frequency Division Multiple Access (OFDMA) in LEO satellite communication networks. A heuristic-based software simulation environment is developed to model a satellite constellation system in Walker Delta form and evaluate the comparative performance of these two multiple access techniques. The study primarily focuses on Signal-to-Interference-plus-Noise Ratio (SINR), system capacity, data rates, spectral efficiency, and varying satellite constellation network conditions. By conducting comprehensive simulations, this research aims to provide insights into the suitability of NOMA and OFDMA for LEO constellations for IoT applications and high-speed internet service in Ka-band. The findings contribute to the ongoing efforts to enhance access strategies for next-generation satellite networks.